[BIOTRANSPLANTLETTERHEAD]

**Exhibit 10.8**

April4, 1991

Dr. Elliot Liebowitz143 Gardner RoadBrookline, MA 02146

Dear Elliot:

             Thiswill confirm our offer to you to join BioTransplant, Inc. on the followingterms:
| 1.     | Title:           | President  and Chief Executive Officer BioTransplant, Inc.  Reporting to the Board.                                                                                                                                                                                                                                                                                          |
|--------|------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|   |             |                                                                                                                                                                                                                                                                                                                                                                              |
| 2.     | Term  of Offer:  | This  offer is contingent on your starting employment no later than May 1, 1991.                                                                                                                                                                                                                                                                                                  |
|   |             |                                                                                                                                                                                                                                                                                                                                                                              |
| 3.     | Compensation:    | $155,000  per year.  Annual bonus of up to 30%  of salary, payable on December 31 in accordance with goals set by the Board.                                                                                                                                                                                                                                                 |
|   |             |                                                                                                                                                                                                                                                                                                                                                                              |
| 4.     | Benefits:        | Health  benefits as provided by the company.                                                                                                                                                                                                                                                                                                                                      |
|   |             |                                                                                                                                                                                                                                                                                                                                                                              |
| 5.     | Equity:          | Common  stock granted at $0.01 per share equal to 5.0% of the founding capitalization  of the Company vested over 4 years beginning with the first anniversary of  employment.  Stock is subject to  repurchase at cost if terminated for cause.   Eligible for consideration for future stock options at the end of each  year subject to the discretion of the Board. |
|   |             |                                                                                                                                                                                                                                                                                                                                                                              |
| 6.     | Severance:       | In  the event of an involuntary separation from BioTransplant, you would receive  6 months base salary, payable in 6 equal installments.                                                                                                                                                                                                                                          |
|   |             |                                                                                                                                                                                                                                                                                                                                                                              |
| 7.     | Confidentiality: | A  standard confidentiality agreement will be executed.                                                                                                                                                                                                                                                                                                                           |

             Ifthese terms are acceptable, please sign and return one copy of this agreement.

             Weare delighted at the prospect of your joining the company.

             Bestregards.
|   | Sincerely,            |
|--------|-----------------------|
|   |                  |
|   | /s/  Harold R. Werner |
|   |                       |
|   | Harold  R. Werner     |
|   | Director              |
|   | BioTransplant,  Inc.  |

 

HRW:dv

AGREED TO:
| By:    | /s/  Elliot Lebowitz  |   | DATE:  | April 7, 1991 |
|--------|-----------------------|--------|--------|---------------|
|   | Dr.  Elliot Liebowitz |   |   |          |